U.S. patent number 5,880,553 [Application Number 08/856,925] was granted by the patent office on 1999-03-09 for electronic component and method of producing same.
This patent grant is currently assigned to Murata Manufacturing Co.,Ltd.. Invention is credited to Choichiro Fujii, Takashi Hashimoto, Makoto Irie, Hidemasa Iwami, Takashi Iwamoto, Hiroyuki Kawakami, Michinobu Maesaka, Motoyuki Okeshi, Ken Taniguchi.
United States Patent |
5,880,553 |
Okeshi , et al. |
March 9, 1999 |
Electronic component and method of producing same
Abstract
An electronic component has a substantially reduced size and is
adapted to be produced at low costs without variation in superior
quality of the component because of the ease of achieving
electrical connection between a piezoelectric element and a
electrode pattern on a substrate supporting the piezoelectric
element. The piezoelectric element has a lower electrode formed on
the lower surface thereof and an upper electrode formed on the
upper surface thereof. The piezoelectric element is fixed to the
substrate such that the lower electrode is bonded to an electrode
provided on the substrate by a conductive adhesive. A conductive
wire is fixed to the upper electrode of the piezoelectric element.
A metallic cap is bonded to the substrate so as to cover and seal
the piezoelectric element on the substrate. The cap is contacted at
its inner surface by the wire, whereby an electrical connection is
achieved between the cap and the upper electrode of the
piezoelectric element. Input and output lead terminals are
connected to the electrodes on the substrate, while a grounding
lead terminal is connected to the cap.
Inventors: |
Okeshi; Motoyuki (Shiga-ken,
JP), Taniguchi; Ken (Moriyama, JP),
Hashimoto; Takashi (Toyama, JP), Irie; Makoto
(Toyama, JP), Kawakami; Hiroyuki (Toyama-ken,
JP), Fujii; Choichiro (Kyoto, JP), Maesaka;
Michinobu (Omihachiman, JP), Iwami; Hidemasa
(Omihachiman, JP), Iwamoto; Takashi (Otsu,
JP) |
Assignee: |
Murata Manufacturing Co.,Ltd.
(Kyoto-fu, JP)
|
Family
ID: |
27319205 |
Appl.
No.: |
08/856,925 |
Filed: |
May 15, 1997 |
Foreign Application Priority Data
|
|
|
|
|
May 15, 1996 [JP] |
|
|
8-146585 |
Aug 9, 1996 [JP] |
|
|
8-227416 |
Dec 3, 1996 [JP] |
|
|
8-339072 |
|
Current U.S.
Class: |
310/352; 310/344;
310/354 |
Current CPC
Class: |
H03H
9/56 (20130101); H01L 41/0475 (20130101); H03H
9/1014 (20130101); H03H 9/562 (20130101); H03H
9/176 (20130101); H03H 9/0514 (20130101); H03H
9/58 (20130101); H03H 9/581 (20130101); H01L
2224/48227 (20130101); H01L 2224/48091 (20130101); H01L
2224/48464 (20130101); Y10T 29/42 (20150115); H01L
2224/48465 (20130101); H01L 2224/45144 (20130101); Y10T
29/4921 (20150115); H01L 2224/4848 (20130101); H01L
2224/48091 (20130101); H01L 2924/00014 (20130101); H01L
2224/48465 (20130101); H01L 2224/48227 (20130101); H01L
2924/00 (20130101); H01L 2224/48465 (20130101); H01L
2224/48091 (20130101); H01L 2924/00 (20130101); H01L
2224/45144 (20130101); H01L 2924/00 (20130101) |
Current International
Class: |
H01L
41/047 (20060101); H03H 9/125 (20060101); H03H
9/05 (20060101); H03H 9/13 (20060101); H03H
9/10 (20060101); H03H 9/58 (20060101); H01L
41/00 (20060101); H03H 9/00 (20060101); H01L
041/08 () |
Field of
Search: |
;310/344,348,351,352,354,355 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Budd; Mark O.
Attorney, Agent or Firm: Graham & James LLP
Claims
What is claimed is:
1. An electronic component comprising:
a substrate having a pattern electrode disposed thereon;
a circuit element mounted on said substrate and including at least
one electrode; and
a cap connected to said substrate so as to cover and seal said
circuit element and so as to define a sealed inner cavity between
said substrate and a periphery of said cap and such that said
pattern electrode on said substrate extends outside of said cap and
said sealed inner cavity; wherein
a conductive portion is provided on said cap and is made of
electrically conductive metal, said conductive portion being
connected to said at least one electrode of said circuit element at
a location inside of said cap and said sealed inner cavity and
connected to said pattern electrode on said substrate at a location
outside of said cap and said sealed inner cavity, whereby said at
least one electrode of said circuit element is electrically
connected to said pattern electrode on said substrate through said
conductive portion of said cap.
2. An electronic component according to claim 1, wherein said
circuit element is an element which uses piezoelectric vibration
and said conductive portion of said cap is connected to a portion
of said at least one electrode of said circuit element near a nodal
point of piezoelectric vibration.
3. An electronic component, comprising:
a substrate having at least first and second electrodes disposed on
a surface thereof;
a circuit element having first and second electrodes each disposed
on one of upper and lower surfaces thereof, said first electrode of
said circuit element being disposed on the lower surface and being
electrically connected to said first electrode disposed on said
substrate; and
a cap connected to said substrate so as to cover and seal said
circuit element and so as to define a sealed inner cavity between
said substrate and a periphery of said cap and such that said
second electrode on said substrate extends outside of said cap and
said sealed inner cavity; wherein
a conductive portion is provided on said cap and is made of
electrically conductive metal, said conductive portion being
electrically connected to said second electrode of said circuit
element which is disposed on the upper surface of said circuit
electrode at a location inside of said cap and said sealed inner
cavity and also to said second electrode of said substrate at a
location outside of said cap and said sealed inner cavity, whereby
said first electrode of said circuit element disposed on the upper
surface of said circuit element is electrically connected to said
second electrode of said substrate through the conductive portion
of said cap.
4. An electronic component according to claim 3, wherein said
circuit element is an element which uses piezoelectric vibration
and said conductive portion of said cap is connected to a portion
of one of said first and second electrodes of said circuit element
near a nodal point of piezoelectric vibration.
5. A piezoelectric component, comprising:
a substrate having a least one electrode disposed on an upper
surface thereof;
a piezoelectric element having first and second electrodes each
disposed on one of upper and lower surfaces thereof, the
piezoelectric element being mounted on said substrate, said first
electrode being disposed on the lower surface of said piezoelectric
element and being electrically connected to said at least one
electrode disposed on said substrate;
a cap connected to said substrate so as to cover and seal said
piezoelectric element; and
a conductive wire provided on said second electrode of said
piezoelectric element which is disposed on the upper surface of
said piezoelectric element, the conductive wire being arranged to
have a loop configuration with both ends of the wire loop being
connected to one of said second electrode and said cap and a curved
portion of said wire loop located between both ends of said wire
loop being disposed in contact with the other one of said second
electrode and said cap;
said cap being arranged so as to cover said piezoelectric element
while making contact at the inner surface thereof with said
conductive wire, whereby said second electrode disposed on the
upper surface of said piezoelectric element is electrically
connected to said cap through said conductive wire.
6. A piezoelectric component according to claim 5, wherein a
conductive adhesive is located at a portion of the inner surface of
said cap so as to contact said conductive wire.
7. A piezoelectric component according to claim 4, wherein said one
of said first and second electrodes of said substrate extends
externally through a region where said cap is bonded to said
substrate, said piezoelectric component further comprising a first
lead terminal connected to an externally led portion of said at
least one electrode of said substrate and a second lead terminal
connected and fixed to an outer surface of said cap.
8. A piezoelectric component according to claim 4, wherein said
substrate has an input/output electrode and a grounding electrode
disposed thereon, said input/output electrode and said grounding
electrode extending externally through a region where said cap is
connected to said substrate, said first electrode of said
piezoelectric element disposed on the lower surface of said
piezoelectric element being connected to said input/output
electrode, said cap being connected to the grounding electrode.
9. An electronic component, comprising:
a substrate having pattern electrodes disposed thereon;
a circuit element mounted on the surface of said substrate and
having electrodes electrically connected to said pattern
electrodes;
a cap bonded to the surface of said substrate so as to cover and
seal said circuit element and so as to define a sealed inner cavity
between said substrate and a periphery of said cap and such that
said second electrode on said substrate extends outside of said cap
and said sealed inner cavity; and
lead terminals electrically connected to portions of said pattern
electrodes which extend externally of said cap; wherein
said cap is made of an electrically conductive material and is
electrically connected to one of the electrodes of said circuit
element and with at least one of said lead terminals at a location
outside of said cap and said sealed inner cavity.
10. A connecting structure for an electronic component,
comprising:
an electronic component having an electrode disposed thereon;
a loop wire disposed on said electrode such that both ends of said
loop wire are connected to said electrode;
a cap for covering said electronic component, the cap being
electrically connected to said loop wire, said loop wire being
arranged such that a curved portion of said loop wire located
between said both ends of said loop wire is arranged to physically
contact said cap; and
a conductive member located between said cap and said curved
portion of said loop wire to electrically connect said loop wire to
said cap.
11. An electronic component according to claim 1, wherein said
pattern electrode is disposed along only one surface of said
substrate.
12. An electronic component according to claim 1, further
comprising an adhesive located at a point where said cap and said
pattern electrode contact each other.
13. An electronic component according to claim 1, wherein said cap
includes a projection which extends toward said circuit element and
is disposed in contact with said at least one electrode of said
circuit element.
14. An electronic component according to claim 3, wherein said
pattern electrode is disposed along only one surface of said
substrate.
15. An electronic component according to claim 3, further
comprising an adhesive located at a point where said cap and said
pattern electrode contact each other.
16. An electronic component according to claim 3, wherein said cap
includes a projection which extends toward said circuit element and
is disposed in contact with said at least one electrode of said
circuit element.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic component such as,
for example, a piezoelectric component and, more particularly but
not exclusively, to a surface-mount type electronic component. The
present invention also relates to a method of producing such an
electronic part.
2. Description of the Related Art
A surface-mount type electronic component, specifically a
piezoelectric component, of the type shown in FIGS. 1 and 2 is
known. This electronic component incorporates an element 4 which
makes use of piezoelectric vibration (referred to as "piezoelectric
element"). The piezoelectric element 4 includes electrodes 4a and
4b disposed on upper and lower major surfaces thereof and is
arranged to vibrate in a longitudinal vibration mode. Pattern
electrodes 2 and 3 are provided on a substrate 1 which supports the
piezoelectric element 4. The lower electrode 4b disposed on the
lower major surface of the piezoelectric element 4 is connected and
fixed to a first one 2 of the pattern electrodes by a conductive
adhesive 5. The upper electrode 4a disposed on the upper major
surface of the piezoelectric element 4 is connected to the other
pattern electrode 3 by a wire 6. A cap 7 is attached to the upper
surface of the substrate 1 so as to cover and seal the
piezoelectric element 4.
In the piezoelectric component shown in FIG. 1, the upper electrode
4a of the piezoelectric element 4 and the pattern electrode 3
disposed on the substrate 1 are connected to each other by a wire
bonding technique. It has been difficult, however, to optimize the
wire-bonding process and resulting structural arrangement due to
the difference in height or vertical location between the electrode
4a of the piezoelectric element 4 and the pattern electrode 3
disposed on the substrate 1.
When a capillary is moved while the wire 6 is being connected to
one of these electrodes 3 and 4a, it is necessary to optimize the
length of feed of the wire 6. If a feed length of the wire 6 is too
small, the wire 6 may contact an edge of the piezoelectric element
4 as shown in FIG. 3, resulting in troubles such as cutting of the
wire 6 or impairment of the electrical characteristics of the
piezoelectric element 4. Conversely, if the feed length of the wire
6 is too large, this causes problems such as the wire 6 sagging
downwardly as shown in FIG. 4, with the result that the wire 6
contacts the piezoelectric element 4 to impair electrical
characteristics of the element 4.
For these reasons, mass-production of electronic components
requiring wire bonding involves great manufacturing difficulty and
experiences significant fluctuation of the quality.
Another problem is that the size of the electronic component must
be large because of the need to provide a space between the
substrate 1 and the cap 7 for accommodating the wire 6 which
interconnects the upper electrode 4a of the piezoelectric element 4
and the pattern electrode 3 disposed on the substrate 1.
In the meantime, electronic components having lead terminals suffer
from the following problem. In general, an electronic component,
specifically of the type in which a circuit element is sealed with
a resin without being constrained by the resin, has such a
structure as that disclosed in Japanese Patent Publication No.
1-48695, wherein lead terminals are electrically connected to the
corresponding electrodes of the circuit element and, after the
circuit element is enclosed in a case with the lead electrodes
extending externally through openings formed in the case wall,
these openings are sealed by a sealing resin.
This type of structure, however, requires that different design
configurations of the openings be provided in conformity with the
shapes of the lead terminals, at the time of design of the
products. In addition, it is necessary to apply a sealing resin to
each of the openings in a one-by-one fashion. This causes an
impediment to mass-production of the electronic parts, thus raising
the costs of production.
Prior to the application of the sealing resin, since the lead
terminals are directly connected to the circuit element, any load
or external force tends to be directly transmitted to the circuit
element, often resulting in breakage or cracking of the circuit
element especially when the circuit element is a fragile one such
as a piezoelectric element. Consequently, throughput is lowered and
the number of acceptable components manufactured is substantially
reduced.
SUMMARY OF THE INVENTION
The preferred embodiments of the present invention provide an
electronic component which allows for easy electrical connection
between a circuit element and an electrode pattern on a substrate
supporting the circuit element, thus providing stabilization of
quality of the electronic components at reduced costs, as well as
reduction in the size of the electronic component. The preferred
embodiments of the present invention also provide a method for
producing such an electronic component having these advantages.
The preferred embodiments of the present invention also provide an
electronic component which is easily mass-producible at low costs
and which has a structure which allows for completely sealing a
circuit element of the electronic component while suppressing an
application of load to the circuit element to prevent damage to the
circuit element and deterioration of the electrical characteristics
of the electronic component.
According to one preferred embodiment of the present invention, an
electronic component comprises: an insulating substrate having an
electrode pattern provided thereon; a circuit element mounted on
the insulating substrate; and a cap bonded to the substrate so as
to cover and seal the circuit element; wherein a conductive portion
is provided on at least the inner surface of the cap, the
conductive portion being connected to an electrode of the circuit
element and also to the electrode pattern on the substrate, whereby
the electrode of the circuit element is electrically connected to
the electrode pattern on the substrate through the conductive
portion of the cap.
In accordance with the preferred embodiments of the present
invention, the cap preferably is used as a part of the electrical
connection, for the purpose of achieving electrical connection
between an electrode of the circuit element and the electrode
pattern provided on the substrate. This connecting method
considerably facilitates the establishment of an electrical
connection between the circuit element and the electrode pattern on
the substrate, as compared with the wire bonding method which has
previously been used, thereby contributing to reduction in the
costs and stabilization of the quality of the electronic component
being manufactured. Furthermore, the size of the cap and, hence,
the size of the whole electronic component, can be reduced because
of elimination of the necessity for providing a wiring space which
has previously been required in order to establish electrical
connection between the electrode on the surface of the circuit
element and the electrode on the substrate.
The conductive portion of the cap may be provided by forming the
whole cap from a metallic material such as aluminum, copper or the
like. Alternatively, the cap may be formed from an insulating
material such as ceramics or resin, and a conductive film may be
disposed at least on the inner surface of the cap by a suitable
technique such as sputtering, evaporation deposition, printing or
the like.
When the circuit element is a piezoelectric element which is
provided at its upper and lower major surfaces with electrodes and
which makes use of piezoelectric vibration, the arrangement is
preferably such that the connection to the conductive portion of
the cap is made at a region of the electrode on the upper surface
of the circuit element near a nodal point of the vibration. Such an
arrangement does not inhibit vibration of the piezoelectric element
and, therefore, does not impair the electrical characteristics of
the electronic component, because the conductive material which
interconnects the conductive portion of the cap and the electrode
on the surface of the piezoelectric element is preferably located
in a region near the nodal point which is free of vibration.
In general, there are a plurality of vibration modes of
piezoelectric vibration, such as longitudinal vibration mode,
radial vibration mode, and so forth. In each of these modes, the
nodal point is located at the centers of the upper and lower
surfaces of the piezoelectric substrate. It is therefore preferred
that the piezoelectric element is fixed to the substrate
substantially at the approximate center of the lower surface
thereof and is connected to the cap inner surface substantially at
the approximate center of the upper surface thereof.
The electronic component in accordance with the preferred
embodiments of the present invention is preferably but not
exclusively a piezoelectric component.
According to another preferred embodiment of the present invention,
there is provided a piezoelectric component, comprising: a
substrate having an electrode disposed on the upper surface
thereof; a piezoelectric element having electrodes disposed on
upper and lower major surfaces thereof and mounted on the
substrate, the electrode on the lower surface of the piezoelectric
element being electrically connected to the electrode on the
substrate; and a cap made of a metallic material and bonded to the
substrate so as to cover and seal the piezoelectric element; and a
conductive wire provided on the electrode on the upper surface of
the piezoelectric element; the cap being placed so as to cover the
piezoelectric while making contact at the inner surface thereof
with the conductive wire, whereby the electrode on the upper
surface of the piezoelectric element is electrically connected to
the cap through the conductive wire.
According to still another preferred embodiment of the present
invention, there is provided a method of producing a piezoelectric
component of the type having a substrate with an electrode disposed
thereon, a piezoelectric element having electrodes provided on
upper and lower surfaces thereof and mounted on the substrate, and
a cap bonded to the substrate so as to cover and seal the
piezoelectric element, the method comprising the steps of: fixing
the piezoelectric element on the substrate such that the electrode
on the lower surface of the piezoelectric element is connected to
the electrode of the substrate; fixing a conductive wire to the
electrode on the upper surface of the piezoelectric element;
applying a conductive adhesive to the portion of the inner surface
of the cap for contacting with the conductive wire; applying a
sealing adhesive to an opening of the cap; placing the cap on the
substrate such that the conductive wire contacts the inner surface
of the cap to cause a portion of the conductive wire to contact
with the conductive adhesive; and simultaneously curing the sealing
resin and the conductive adhesive.
In these preferred embodiments of the present invention, electrical
connection between the electrode disposed on the upper surface of
the piezoelectric element and the cap is preferably achieved by a
wire which is fixed on the electrode on the upper surface of the
piezoelectric element and which is pressed against the inner
surface of the cap. The wire may be formed by a known technique
such as that used in wire bonding technique. If the position at
which the wire is fixed to the piezoelectric element is determined
to be the vibration-free portion of the piezoelectric element,
there is no substantial risk that the vibration is impeded, unlike
the case where a conductive adhesive used as the connecting
material is spread over a wide area to impede vibration of the
piezoelectric element. In addition, any thermal stress produced as
a result of difference in thermal expansion between different
materials is effectively absorbed by the elastic nature of the
wire, so that electrical conduction can stably be maintained with a
high degree of reliability. The elastic nature of the wire also
serves to absorb any fluctuation in the size of the gap between the
cap and the piezoelectric element, which provides a greater
tolerance in the administration of dimensions.
Preferably, the wire has a loop-like form and is preferably fixed
at both ends to the electrode on the upper surface of the
piezoelectric element. Such a loop shape provides a large
elasticity so as to ensure stable contact between the cap and the
wire. The loop-shaped wire can withstand long use with reduced risk
of cutting or sagging down, thus offering a high degree of
reliability and eliminating the problems of the prior art wire
connections. The wire may be formed by using a known technique such
as that used in a wire bonding method. Since the points on the
electrode on the upper surface of the piezoelectric element to
which the ends of the loop-shaped wire are connected are almost at
the same vertical level, an optimum condition for achieving
electrical connection can be determined without difficulty.
Preferably, the whole cap is made of a metallic material having
excellent electrical conductivity, such as aluminum, copper or the
like.
The piezoelectric element may be adapted to vibrate in any
vibration mode. It is, however, preferred that the wire is fixed to
a portion of the piezoelectric element which is free of vibration
or a region near such a vibration-free point. In case of a
piezoelectric element having a nodal point, e.g., a piezoelectric
element using longitudinal vibration mode or radial vibration mode,
it is recommended that the wire is fixed to such a nodal point.
Similarly, the portion of the lower side of the piezoelectric
element at which the element is fixed to the substrate electrode
should be a portion which is free of vibration.
Although electrical connection can be achieved merely by bringing
the cap into contact with the wire, it is preferred that a
conductive adhesive be applied to the portion of the cap inner
surface where the contact with the wire occurs, if a specifically
low level of resistance and high level of reliability are desired.
In such a case, the amount of the conductive adhesive to be applied
should be determined such that the adhesive contacts with the wire
alone, i.e., the adhesive does not contact the piezoelectric
element, in order to avoid restriction of vibration of the
piezoelectric element.
Preferably, the electrode on the substrate extends externally and a
first lead terminal is connected to this externally led portion of
the substrate electrode, while a second lead terminal is connected
and fixed to the outer surface of the cap. In this case, the
electrode disposed on the upper surface of the piezoelectric
element is preferably directly connected to the lead terminal
through the cap, without using the intermediary of the electrode on
the substrate, whereby a piezoelectric component of the
lead-terminal type having a simple construction for external
connection can be obtained.
It is also possible to obtain a surface-mount type piezoelectric
component, by forming an input/output electrode and a grounding
electrode on the substrate and externally extending the electrodes
through a region where the cap is bonded, with the input/output
electrode connected to the electrode on the lower side of the
piezoelectric element, while connecting the cap to the grounding
electrode.
According to a further preferred embodiment of the present
invention, there is provided an electronic part, comprising: an
insulating substrate having pattern electrodes provided thereon; a
circuit element mounted on the surface of the substrate and having
electrodes electrically connected to the pattern electrodes; a cap
bonded to the surface of the substrate so as to cover and seal the
circuit element; and lead terminals electrically connected to
portions of the pattern electrodes which extend externally from the
cap; wherein the cap is made of an electrically conductive material
and is electrically connected to one of the electrodes of the
circuit element and with at least one of the lead terminals.
These and other elements, features, and advantages of the preferred
embodiments of the present invention will be apparent from the
following detailed description of the preferred embodiments of the
present invention, as illustrated in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an electronic component having
problems to be overcome by the preferred embodiments of the present
invention;
FIG. 2 is a sectional view of the electronic component taken along
the line A--A of FIG. 1;
FIG. 3 is a sectional view of the electronic component taken along
the line A--A of FIG. 1, illustrative of an example of wiring
failure;
FIG. 4 is a sectional view of the electronic component taken along
the line A--A of FIG. 1, illustrative of another example of wiring
failure;
FIG. 5 is a perspective view of a first preferred embodiment of the
electronic component in accordance with the present invention;
FIG. 6 is a sectional view of the electronic component taken along
the line B--B of FIG. 5;
FIG. 7 is a sectional view of a second preferred embodiment of the
electronic component in accordance with the present invention;
FIG. 8 is a sectional view of a third preferred embodiment of the
electronic component in accordance with the present invention;
FIG. 9 is a sectional view of a fourth preferred embodiment of the
electronic component in accordance with the present invention;
FIG. 10 is a sectional view of a fifth preferred embodiment of the
electronic component in accordance with the present invention;
FIG. 11 is a sectional view of a sixth preferred embodiment of the
electronic component in accordance with the present invention;
FIG. 12 is a sectional view of a seventh preferred embodiment of
the electronic component in accordance with the present
invention;
FIG. 13 is an exploded perspective view of a piezoelectric filter
as an eighth preferred embodiment of the present invention;
FIG. 14 is a perspective view of the lower side of a piezoelectric
element;
FIG. 15 is an enlarged view of the eighth preferred embodiment
showing particularly the structure for securing a wire;
FIG. 16 is an enlarged view of the eighth preferred embodiment
showing particularly the structure for connecting a wire and a
cap;
FIG. 17 is a perspective view of the piezoelectric filter with an
external cover attached thereto;
FIG. 18 is an exploded perspective view of a piezoelectric filter
as a ninth preferred embodiment of the present invention;
FIG. 19 is a perspective view of a tenth preferred embodiment of
the present invention;
FIG. 20 is a sectional view of the tenth preferred embodiment,
taken along the line B--B of FIG. 19;
FIG. 21 is a perspective view of a modification of the tenth
preferred embodiment;
FIG. 22 is a perspective view of another modification of the tenth
preferred embodiment;
FIG. 23 is a perspective view of the lower surface of the
electronic part shown in FIG. 22; and
FIG. 24 is a fragmentary side elevational view of the electronic
part shown in FIG. 22.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
FIGS. 5 and 6 show an electronic component as the first preferred
embodiment of the present invention. As in the case of the
electronic component shown in FIG. 1 described before, the
electronic component shown in FIGS. 5 and 6 has a substrate 10, a
piezoelectric element 20 and a cap 30.
The substrate 10 is preferably a substantially rectangular thin
sheet member made of an alumina ceramics, a glass epoxy resin, or
the like. A pair of pattern electrodes 11, 12 are disposed on the
upper surface of the substrate 10 by a known technique such as
sputtering, evaporation, printing or the like. One 11 of the
electrodes has an external connecting portion 11a which is formed
to extend preferably in a belt-like arrangement along one shorter
side of the substrate 10, and an internal connecting portion 11b
which extends inwardly towards the center of the substrate 10 from
the external connecting portion 11a substantially perpendicularly
thereto. The other electrode 12 is arranged in a belt-like
arrangement so as to extend along the other shorter side of the
substrate 10.
A frame-shaped insulating layer 13, e.g., an insulating resist
pattern, is provided on the upper surface of the substrate 10 so as
to overlie the electrodes 11, 12. The internal connecting portion
11b of one of the pattern electrodes 11 is exposed at the central
open area of the insulating layer 13. The insulating layer 13
prevents shortcircuiting between the pattern electrode 11 on the
substrate 10 and the metallic cap 30, and also compensates for any
height variation or unevenness of the surface of the substrate 10
caused by the thickness of the electrodes 11, 12, thus preventing
any sealing failure of the cap 30.
The piezoelectric element 20 may be a piezoelectric filter or a
piezoelectric oscillator which is arranged to vibrate in the
longitudinal vibration mode. The piezoelectric element 20 has a
substantially rectangular piezoelectric ceramics plate which
includes electrodes 21, 22 preferably formed so as to extend over
the entire areas of the upper and lower surfaces of the plate. The
central portion of the electrode 21 (referred to as "lower
electrode", hereinafter) disposed on the lower surface of the
piezoelectric element 20 is connected and fixed preferably by a
conductive adhesive 23 to the internal connecting portion 11b of
the pattern electrode 11 which is exposed at the central open area
of the insulating layer 13. To this end, for example, the
conductive adhesive 23 may be applied by a dispenser or by
printing, and the element 20 is placed on the adhesive, followed by
heating at approximately 150.degree. C. for 30 minutes to cause the
conductive adhesive 23 to cure. It is thus possible to fix the
element 20 to the substrate 10, while achieving electrical
connection between the electrode 11 of the substrate 10 and the
lower electrode 21 of the element 20. Small gaps are left between
both ends of the element 20 and the insulating layer 13 so that
these ends of the element 20 do not contact with the insulating
layer 13.
A metallic cap 30 is bonded to the upper surface of the substrate
10 so as to cover and seal the element 20. A suitable material such
as a sealing adhesive 31 is applied to the rim of opening of the
cap 30 at a uniform thickness by transferring method, for example.
A conductive adhesive 32 is preferably applied by a dispenser to
the electrode 22 (referred to as "upper electrode") disposed on the
upper surface of the piezoelectric element 20, preferably to the
nodal point or to a portion in the central region near the nodal
point. The amount of application of the conductive adhesive 32 is
preferably adjusted to accommodate the clearance between the upper
electrode 22 of the element 20 and the inner surface of the cap 30,
such that the adhesive 32 does not excessively spread on the
element 20. When the cap 30 is placed on the substrate 13, the rim
of opening of the cap 30 closely contacts the insulating layer 13
disposed on the substrate 10, while the inner surface of the cap 30
contacts the upper electrode 22 of the element 20 through the
conductive adhesive 32. Both the sealing adhesive 31 and the
conductive adhesive 32 are cured by, for example, a 30-minute
heating at approximately 150.degree. C. It is thus possible to bond
the cap 30 to the substrate 10 in a sealing manner and to achieve
electrical connection between the upper electrode 22 of the element
20 and the cap 30.
In this preferred embodiment, since the sealing adhesive 31 is
electrically insulating and since an insulating layer 13 is formed
on the portion of the substrate 10 where the cap is to be bonded,
electrical insulation is ensured between the cap 30 and the
electrode 11 of the substrate 10. The sealing adhesive 31, however,
may be a conductive adhesive.
After the bonding of the cap 30, a conductive adhesive 33 is
preferably applied by a dispenser to the external surface of the
cap 30 and the electrode 12 on the substrate 10. The conductive
adhesive 33 is cured by heating similar to that stated above,
whereby an electrical connection is achieved between the cap 30 and
the electrode 12 on the substrate 10.
The application of the conductive adhesive 33 may be done before
the heat curing of the sealing adhesive 31 and the conductive
adhesive 32, so that the conductive adhesive 33 is heated and cured
simultaneously with the sealing adhesive 31 and the conductive
adhesive 32.
The lower electrode 21 of the piezoelectric element 20 is
electrically connected to the pattern electrode 11 of the substrate
10 via the conductive adhesive 23, while the upper electrode 2 of
the same is electrically connected to the pattern electrode 12 on
the substrate 10 via the conductive adhesive 32, cap 30 and the
conductive adhesive 33, whereby a surface-mount type piezoelectric
component is completed.
The process for achieving electrical connection between the
piezoelectric element 20 and the pattern electrode 12 of the
substrate can be done in a multiplexing manner for a large number
of products, because the connection can be achieved simply by
applying the conductive adhesive 32. The application of the
conductive adhesive 32 can be done without generating or imparting
any substantial impact which, when a wire bonding technique is used
as in conventional components and processes, would be applied to
the element 20. It is thus possible to attain higher efficiency for
achieving electrical connection, while preventing damage to the
element 20.
In this preferred embodiment, it is possible to eliminate the use
of wire connections and the step of wire bonding completely.
Consequently, high product quality is reliably obtained, because
degradation which previously has been inevitable due to fluctuation
in wire connections and wire bonding is avoided. The elimination of
wiring also contributes to reduction in the overall size of the
electronic component.
FIG. 7 shows an electronic part according to a second preferred
embodiment of the present invention. In FIG. 7, the same reference
numerals are used to denote the same parts or members as those of
the first preferred embodiment described in connection with FIG.
6.
The second preferred embodiment features a projection 30a which
projects inwardly preferably from the approximate center of the
metallic cap 30. A cream solder 34 is preferably applied to the
projection 30a. In the assembly of the electronic component of FIG.
7, the cap 30 is placed on the substrate 10 and is heated to a
temperature at which the solder is molten, whereby the cap is
connected to the upper electrode 22 of the element 20 by soldering.
It is possible to use a conductive adhesive in place of the solder
34.
In this preferred embodiment, since the conductive agent (solder or
conductive adhesive) 34 is concentrated on the projection 30a,
undesirable spreading of the agent 34 over the element 20 can be
prevented, despite any fluctuation in the amount of the agent 34
applied or fluctuation in the size of the clearance between the
upper electrode 22 of the piezoelectric element 20 and the inner
surface of the cap 30.
FIG. 8 shows an electronic part according to a third preferred
embodiment of the present invention. In FIG. 8, the same reference
numerals are used to denote the same parts or members as those of
the first preferred embodiment described in connection with FIG.
6.
The third preferred embodiment has an electrically conductive
spring member 35 which is fixed preferably by welding to the
central portion of the inner surface of the cap 30, while the other
ends of the spring member 35 resiliently contact the approximate
central portion of the upper electrode 22, thus achieving the
electrical connection. In the production of this electronic part,
it is preferred to apply a force to keep the cap 30 in contact with
the substrate 10 until the adhesive is cured, in order to prevent
the cap 30 from being moved apart from the substrate 10 by the
force of the spring member 35.
In the third preferred embodiment as described, the electrical
connection between the piezoelectric element 20 and the cap 30 can
be achieved without requiring any heat treatment, so that influence
of heat on the element 20 can be reduced. In addition, since the
spring member 35 effectively absorbs any fluctuation of the size of
clearance between the piezoelectric element 20 and the cap 30,
greater tolerance is afforded for the dimensions of the cap 30.
A conductive tape 36 may be used in place of the conductive
adhesive for achieving electrical connection between the cap 30 and
the pattern electrode 12.
FIG. 9 shows an electronic part according to a fourth preferred
embodiment of the present invention. In FIG. 9, the same reference
numerals are used to denote the same parts or members as those of
the first preferred embodiment described in connection with FIG.
6.
The fourth embodiment features a substantially U-shaped conductive
wire 37 which is fixed preferably by welding at both ends thereof
to an approximate central portion of the inner surface of the cap
30, with the central apex portion of the U-shaped wire 37
resiliently pressed onto a central region of the upper electrode 22
of the piezoelectric element 20. The wire 37 may be fixed to the
inner surface of the cap 30 by suitable known means such as a wire
bonder. This fourth preferred embodiment offers the same advantages
as those presented by the third preferred embodiment.
FIG. 10 shows an electronic component according to a fifth
preferred embodiment of the present invention. In FIG. 10, the same
reference numerals are used to denote the same parts or members as
those of the first preferred embodiment described in connection
with FIG. 6.
The fifth preferred embodiment features a conductive tape 38 which
is used for achieving electrical connection between the metallic
cap 30 and the upper electrode 22 of the piezoelectric element 20.
The flexible nature of the conductive tape 38 is effectively used
for accommodating any fluctuation in the size of the clearance
between the piezoelectric element 20 and the inner surface of the
cap 30.
The fifth preferred embodiment shown in FIG. 10 also eliminates
wire bonding and therefore provides the same advantages as provided
by the first preferred embodiment shown in FIGS. 5 and 6. This
fifth preferred embodiment also offers the same advantages as those
produced by the third preferred embodiment. In addition, problems
such as cracking of the piezoelectric element 20 are eliminated
because no pressure is applied to the piezoelectric element 20.
Instead, the pressure is absorbed by the conductive tape 38.
FIG. 11 shows an electronic component according to a sixth
preferred embodiment of the present invention. In FIG. 11, the same
reference numerals are used to denote the same parts or members as
those of the first preferred embodiment described in connection
with FIG. 6.
In the sixth preferred embodiment, a cap 41 is preferably formed of
an insulating material such as alumina ceramics, resin or other
suitable insulating material. A conductive portion 42 is formed on
the inner surface of the cap 41 so as to extend from the
approximate center to one end of the cap 41, by sputtering,
evaporation deposition or other known technique. On the other hand,
a preferably frame-shaped insulating layer 43 is disposed on the
substrate 10. The insulating layer 43 has a small width which is
substantially equal to the thickness of the wall of the cap 41.
A sealing adhesive 31 is applied to the opening rim of the cap 41
by, for example, transferring method. A conductive adhesive 44 is
applied preferably by a dispenser to one end of the conductive
portion 42 which extends to the open end of the cap 41. A
conductive adhesive 45 is applied to the other end of the
conductive portion 42 which is preferably located at the
approximate center of the cap 41.
As the cap 41 is placed on the substrate 10, the cap 41 is bonded
to the insulating layer 43 by the sealing adhesive 31, while the
conductive portion 42 of the cap 41 is electrically connected to
the pattern electrode 12 of the substrate 10 by the conductive
adhesive 44. At the same time, the conductive adhesive 45 provides
an electrical connection between the conductive portion 42 of the
cap 41 and the upper electrode 22 of the piezoelectric element 20.
As this assembly is heated to a predetermined temperature, the
sealing adhesive 31 and the conductive adhesives 44, 45 are cured,
whereby the upper electrode 22 of the piezoelectric element 20 is
electrically connected to the pattern electrode 12 via the
conductive adhesive 45, conductive portion 42 of the cap 41 and the
conductive adhesive 44.
Although in the sixth preferred embodiment the conductive portion
42 extends only on the inner surface of the cap 41, the outer end
of the conductive portion 42 may be extended to reach the external
surface of the cap 41. In such a case, electrical connection can
easily be achieved by connecting, via a conductive adhesive, the
pattern electrode 12 to the end of the conductive portion 42 which
is extended and disposed on the external surface of the cap 41.
In this preferred embodiment, the cap 41 is preferably made of a
non-conductive material, so that the electronic part is not
influenced at all by electrical noise even when other part has been
brought into contact with the cap 41. In addition, if the cap 41 is
made of the same material as the substrate 10, the seal between the
cap 41 and the substrate 10 can be maintained despite any change in
temperature, because both the cap 41 and the substrate 10 are made
of the same material and exhibit the same amount of thermal
expansion.
FIG. 12 shows an electronic component according to a seventh
preferred embodiment of the present invention. In FIG. 12, the same
reference numerals are used to denote the same parts or members as
those of the first preferred embodiment described in connection
with FIG. 6.
The seventh preferred embodiment features a substantially U-shaped
wire 39 which is fixed at its both ends to a central region of the
upper surface of the upper electrode 22 of the piezoelectric
element 20 by a wire bonder. A conductive adhesive 40 is preferably
applied to the approximate central region of the inner surface of
the metallic cap 30, such that the conductive adhesive contacts the
wire 39 alone when the cap 30 is placed on the substrate 10.
After the cap 30 is placed on the substrate 10, a heat treatment is
conducted preferably for 30 minutes at, for example, 150.degree.
C., so that the conductive adhesive 40 is cured. Consequently, the
cap 30 and the upper electrode 22 of the piezoelectric element 20
are electrically connected to each other through the wire 39 and
the conductive adhesive 40. The heat curing of the conductive
adhesive 40 may be executed simultaneously with the heat curing of
the sealing adhesive 31 and the conductive adhesive 33.
In this preferred embodiment, the conductive adhesive 40 does not
attach to the piezoelectric element 20, so that electrical
characteristics of the piezoelectric element are never impaired.
Fixing of both ends of the wire 39 can be conducted by a wire
bonder without difficulty, because the points to which these ends
of the wire are to be fixed are located at the same level or
vertical height. The combination of the wire 39 and the conductive
adhesive 40 provides a higher degree of reliability of the
electrical connection than when the wire 39 is used alone. In
addition, the influence of heat on the piezoelectric element 20 can
be reduced because the heat is not directly transmitted to the
piezoelectric element 20 during the heat curing of the conductive
adhesive 40.
The first to seventh preferred embodiments as described are only
illustrative.
For instance, while in the described preferred embodiments, a
single circuit element is connected to the cap as a conductor, the
arrangement may be such that a plurality of circuit elements are
mounted on a substrate and associated electrodes of these circuits
are interconnected by a wire which is held in contact with or
electrically conducted by a conductive adhesive to the conductive
portion of the cap.
The electrode of the circuit element, which is connected to the
pattern electrode of the substrate through the conductive portion
of the cap, may be an input/output electrode or a grounding
electrode. When this electrode is a grounding electrode, the cap,
if made of a metallic material can function as an electromagnetic
shield.
While in the described preferred embodiments, the electrode pattern
formed on the substrate has two electrodes, this is only
illustrative and the preferred embodiments of the present invention
do not exclude the use of three or more electrodes on the
substrate.
Further, although piezoelectric devices such as filters and
oscillators are specifically mentioned, the circuit element of the
electronic part of the preferred embodiments of the present
invention may be other types of elements such as a capacitor or may
be a circuit module.
FIG. 13 shows an AM piezoelectric filter which is a piezoelectric
component according to an eighth preferred embodiment of the
present invention. This piezoelectric filter includes a substrate
110, a piezoelectric element 120, a metallic cap 130 and lead
terminals 140 to 142.
The substrate 110 is a substantially rectangular thin insulating
plate made of alumina ceramics, glass ceramics, glass epoxy resin,
or the like, and is provided at the upper surface thereof with a
pair of pattern electrodes: namely, an input electrode 111 and an
output electrode 112, preferably formed by a known technique such
as sputtering, evaporation deposition, printing or the like. These
electrodes 111 and 112 are preferably formed symmetrically. More
specifically, external connecting portions 111a, 112a of these
electrodes 111, 112 are preferably formed to have belt-like shapes
so as to extend along the shorter sides of the substrate 10, while
internal connecting portions 111b, 112b of the same extend towards
the center of the substrate 10 so as to oppose each other, from the
external connecting portions 111a, 112a substantially
perpendicularly thereto.
A frame-shaped insulating layer 113 comprising, for example, a
resist pattern is disposed on the upper surface of the substrate
110 so as to overlie portions of the electrodes 111, 112. The
internal connecting portions 111b, 112b are exposed through the
central opening area 113a of the insulating layer 113. The
insulating layer 113 prevents shortcircuiting between the pattern
electrodes 111, 112 of the substrate 110 and the metallic cap 130
and compensates for any height variation or unevenness of the
surface of the substrate 10 due to thickness of the electrodes 111,
112, thereby eliminating any sealing failure of the cap 130.
The piezoelectric element 120 is preferably a piezoelectric filter
element which is arranged to vibrate in, for example, the
longitudinal vibration mode. The piezoelectric element 120
preferably has a substantially rectangular piezoelectric ceramics
substrate 121 and electrodes 122 (referred to as "lower electrode")
and 123 (referred to as "upper electrode") provided on the lower
and upper surfaces of the piezoelectric ceramics substrate 121. As
is seen from FIG. 14, the lower electrode 122 of the piezoelectric
element 120 is preferably divided by two longitudinal grooves into
three electrodes 122a, 122b and 122c. The central electrode 122b
serves as an input electrode, while both side electrodes 122a, 122c
serve as output electrodes. Small amounts of conductive adhesive
125a to 125c are applied to the above-mentioned electrodes 122a to
122c by a dispenser or by a suitable method such as printing. The
adhesive 125b applied to the input electrode 122b is connected and
fixed to the internal connecting portion 111b of one 111 of the
pattern electrode. The adhesive 125a, 125c applied to the output
electrodes 122a, 122c are connected and fixed to the internal
connecting portion 112b of the other pattern electrode 112. It is
thus possible to fix the element 120 to the substrate 110, while
achieving electrical connections between the electrodes 111, 112 of
the substrate 110 and the lower electrodes 122a, 122b, 122c. In
order to avoid contact between both ends of the element 120 and the
insulating layer 113, slight gaps are formed therebetween.
The upper electrode 123 is formed to cover the entire area of the
upper surface of the piezoelectric element 120. A conductive wire
126 is fixed preferably by wire bonding technique to the
approximate center of the upper electrode 123, i.e., preferably to
a portion of the electrode 123 which is a nodal point of the
longitudinal vibration. Although the illustrated preferred
embodiment employs an Au wire of, for example, 30 .mu.m diameter,
any other suitable wire may be used provided that it provides
required conductivity, resiliency and weather resistance. Wire
bonding usually employs primary and secondary sides. In this
preferred embodiment, however, both the primary side 126a and the
secondary side 126b are secured to the upper electrode 123 as shown
in FIG. 15, in order to obtain high levels of resiliency of the
wire 126 and reliability of the connection. Thus, the wire 126 has
the form of a loop with both ends thereof fixed to the upper
electrode 23. The loop can have any desired height. The height,
however, should be determined taking into account any fluctuation
of the state of mounting of the element 120 and the dimensions of
the cap 130, such that the wire 126 can be pressed against the
inner surface of the cap 130 without failure. In the illustrated
preferred embodiment, the height of the loop is set to about 500
.mu.m, so that the loop is depressed or collapsed at least by about
100 .mu.m in the assembled piezoelectric filter.
The metallic cap 130 is bonded to the substrate 110 so as to cover
and seal the element 120. A suitable agent such as a sealing
adhesive 131 is preferably applied before hand to the opening rim
of the cap 130 so as to form a layer of a uniform thickness by, for
example, transferring method. At the same time, a conductive
adhesive 132 has been applied, by means of a dispenser or by a
suitable method such as pin-transferring method, to the inner
surface of the cap 130, in particular to the portion which opposes
to the wire 126 of the piezoelectric element 120. The amount of the
conductive adhesive 132 to be applied should be carefully adjusted
so as to provide such a thickness of the adhesive layer that the
adhesive 132 makes contact with the wire 126 alone, without
contacting the piezoelectric element 120. As the cap 130 is placed
on the substrate 110, the opening rim of the cap 130 makes close
contact with the insulating layer 113 of the substrate 110, thus
sealing the interior of the cap 130. It will be seen that, when the
cap 130 is placed on the substrate 110, the wire 126 cuts into the
conductive adhesive 132 on the inner surface of the cap 130 and is
then collapsed, as shown in FIG. 16. When heat is applied for a
predetermined time in this state, the sealing adhesive 131 and the
conductive adhesive 132 are cured almost simultaneously, thus
accomplishing seal bonding of the cap 130 to the substrate 110 and
electrical connection between the upper electrode 123 of the
element 120 and the cap 130. Since the conductive adhesive 132 is
spaced apart from the piezoelectric element 120, the heat is not
directly transmitted from the cap 130 to the piezoelectric element
120 under the heat treatment, so that any undesirable effect of
heat on the piezoelectric element 120 is reduced.
The cap 130 made of a metal also exhibits a rise of electrical
resistance in accordance with lapse of time, due to oxidation of
the surface. It is therefore preferred that the conductive portion
is subjected to a surface treatment such as plating with gold. In
this preferred embodiment, since the sealing adhesive 131 is
electrically insulating and since the insulating layer 113 has been
formed on the portion of the substrate 10 where the cap 130 is to
be bonded, electrical insulation is ensured between the cap 130 and
the electrode 111 of the substrate 110.
Input/output lead terminals 140, 141 are connected preferably by
soldering to the external connecting portions 111a, 112a of the
pattern electrodes 111, 112 of the substrate 110. A grounding lead
terminal 142 is fixed to the external surface of the cap 130 by
soldering or welding. When it is desired that the input and output
terminals 140, 141 not be in close proximity to the cap 130, it is
advisable that the external connecting portions 111a, 112a of the
pattern electrodes 111, 112 extend to the underside or bottom
surface of the substrate 110 and the input and output lead
terminals 140, 141 are fixed to these extended portions of the
electrodes 111, 112. The grounding lead terminal 142 may be
connected to the cap 130 in advance of the bonding of the cap 130
to the substrate 110.
After the lead terminals 140 to 142 are connected, an external
coating 145 is provided so as to integrally cover the cap 130 and
the substrate 110, thus completing the piezoelectric component as
the product as shown in FIG. 17.
In the piezoelectric component of this preferred embodiment, the
grounding electrode, i.e., the upper electrode 123, of the
piezoelectric element is electrically connected to the cap 130 via
the wire 126, and the cap 130 is electrically connected to the
grounding lead terminal 142. This eliminates the necessity for a
grounding electrode to be formed on the substrate 110, thus
contributing to reduction in the size of the substrate 110 and
simplification of the process for achieving electrical connections.
In addition, the described preferred embodiment does not require
any wiring which is used in conventional devices for the electrical
connection between the grounding electrode on the substrate and the
piezoelectric element. It is therefore possible to eliminate
problems attributable to use of the wiring, such as difficulty
encountered in setting optimum bonding condition attributable to
difference in the levels or vertical locations of the points to
which the wire is to be bonded, as well as troubles such as cutting
or sagging down of the wire. The elimination of the wiring also
allows the cap to have a reduced size, because there is no need for
providing a wiring space inside the cap.
FIG. 18 shows a surface-mount type piezoelectric filter
incorporating a pair of piezoelectric elements, according to a
ninth preferred embodiment of the present invention.
A substrate 150 has a pattern electrode 151 for input, a pattern
electrode 152 for output, a pattern electrode 153 for grounding,
and an intermediate electrode 154. The input, output and grounding
pattern electrodes 151 to 153 respectively extend to the underside
or bottom surface of the substrate 150, preferably through grooves
150a formed in side edges of the substrate 150. A frame-shaped
insulating layer 155 is preferably disposed on the portion of the
substrate 150 where the cap is to be bonded. Apertures 156 are
formed in two opposing sides of the frame-shaped insulating layer
155, more specifically at portions corresponding to the grounding
electrode 153. A conductive adhesive 157 is preferably applied to
each of the apertures 156.
The piezoelectric filter incorporates a pair of piezoelectric
elements 160, 161 each of which preferably is adapted to vibrate in
a longitudinal vibration mode. As in the case of the eighth
preferred embodiment shown in FIG. 14, the lower electrode (not
shown) formed on the lower side of each piezoelectric element is
preferably segmented into three electrodes by a pair of
longitudinal grooves. The central electrodes, which correspond to
the central electrode 122b shown in FIG. 14, of the respective
piezoelectric elements 160, 161 are connected to the input pattern
electrode 151 and the output pattern electrode 152 of the substrate
150, by means of islands 161, 163 of conductive adhesive,
respectively. Both side electrodes, corresponding to the electrodes
122a, 122c shown in FIG. 14, of the piezoelectric elements 160, 161
are connected to the intermediate electrode 154 by means of islands
164 to 167 of conductive adhesive. Thus, the pair of piezoelectric
elements 160 and 162 are cascade-connected between the input
electrode 151 and the output electrode 152. The upper electrodes
160a, 160b of the piezoelectric elements 160 and 161 are connected
to each other by a bridge-like single wire 168. This wire 168 also
is formed by using wire bonding technique, as in the eighth
preferred embodiment.
The cap 170 preferred has a size large enough to simultaneously
cover both piezoelectric elements 160, 161. A conductive adhesive
171 is applied to the inner surface of the cap 170, particularly to
a portion where the inner surface is to be contacted by the wire
168. A sealing adhesive 172 is applied to the entire opening rim of
the cap 170, so that the opening rim of the cap 170 is bonded to
the substrate 150 as the cap 170 is pressed onto the substrate 150.
In the course of the bonding of the cap rim to the substrate 150,
part of the sealing adhesive 172 is displaced by the conductive
adhesive 157 which has been applied to the apertures 156 and the
opening rim of the cap 170 cuts into the conductive adhesive 157.
At the same time, the top portion of the bridge-like wire 168 cuts
into the conductive adhesive 171 which has been applied to the
inner surface of the cap 170, while the wire 168 is partially
depressed or collapsed. In this state, heat is applied so that the
sealing adhesive 172 and the adhesive islands 157, 162 to 167 and
171 of the conductive adhesive are cured almost simultaneously,
thus accomplishing sealing of the interior of the cap 170, while
establishing the required electrical connections. Namely, the upper
electrodes 160a, 160b of the piezoelectric elements 160, 161 are
connected through the wire 168 to the cap 170 which in turn is
connected to the grounding electrode 153 through the conductive
adhesive 157. Consequently, the upper electrodes 160a, 160b of the
piezoelectric elements 160, 161 are brought into electrical
connection with the grounding electrode 153.
In the ninth preferred embodiment as described, a single wire 168
serves to interconnect the upper electrodes of the pair of
piezoelectric elements 160, 161 to each other and also to connect
these upper electrodes to the cap 170. Such an arrangement,
however, is not exclusive and the arrangement may be such that a
single loop-shaped wire is used for each of the piezoelectric
elements 160, 161. The ninth preferred embodiment as described,
however, is advantageous in that it used only one wire and, hence,
reduces the steps of the work for achieving the connection.
In the described ninth preferred embodiment, a conductive adhesive
157 is preferably applied beforehand to the substrate 150, in order
to achieve electrical connection between the cap 170 and the
grounding electrode 153. However, the preferred ninth embodiment
may be modified such that the grounding electrode 153 and the
external surface of the cap 170 may be connected by a conductive
adhesive or a solder, after bonding the cap 170 to the substrate
150 via the sealing adhesive 172. Other suitable bonding process
also may be employed.
Although a surface-mount type piezoelectric part has been described
in the ninth preferred embodiment, a lead terminal type
piezoelectric part can be obtained by connecting, as in the eighth
preferred embodiment, a lead terminal to the cap 170, while
connecting lead terminals to the input and output terminals 151,
152. In this case, it is not necessary to form a grounding
electrode 153 on the substrate 150. The apertures 156 formed in the
sides of the insulating layer 155 and the conductive adhesive 157
also can be eliminated when the piezoelectric component is
constructed to have such a lead-terminal type structure.
The structure of the ninth preferred embodiment may be applied to a
piezoelectric component which incorporates only one piezoelectric
element. In such an application, an input electrode, an output
electrode and a grounding electrode are disposed on the substrate
150, and the electrode on the lower surface of the single
piezoelectric element is commonly connected and fixed to the input
and output electrodes by a conductive adhesive, while the electrode
on the surface of the piezoelectric element is connected by a wire
to the cap which in turn is connected to the grounding electrode by
means of, for example, a conductive adhesive.
The eighth and ninth preferred embodiments are only illustrative
and may be modified in various forms.
For example, the use of a conductive adhesive for achieving
connection between the piezoelectric element 120 and the substrate
110 is not exclusive and may be substituted by any other known
suitable connecting member or substance.
The configuration of the lower electrode 122 of the piezoelectric
element 120 shown in FIG. 14 also is illustrative. For instance,
instead of segmenting the electrodes into three electrodes by two
longitudinal grooves as illustrated, the electrode may be split
into two electrodes by a single longitudinal groove, or a single
solid lower electrode may be used without any dividing groove.
Thus, the eighth and ninth preferred embodiments can be used not
only for piezoelectric parts of the type having three electrodes
but also to piezoelectric parts of the type having two
terminals.
In these preferred embodiments, the upper electrode of the
piezoelectric element connected to the cap serves as a grounding
electrode, so that the metallic cap plays also the role of an
electromagnetic shield. However, the described preferred
embodiments may be modified such that the upper electrode of the
piezoelectric element connected to the cap serves as an electrode
for purposes other than grounding.
Furthermore, the eighth and ninth preferred embodiments are
applicable also to oscillators, although piezoelectric filters have
been specifically described.
As will be understood from the foregoing description, in the eighth
and ninth preferred embodiments of the present invention, the
electrical connection between the upper electrode of the
piezoelectric element and the cap is achieved by pressing the wire
fixed to the upper electrode into contact with the inner surface of
the cap. Therefore, any thermal stress occurring due to difference
in thermal expansion between the piezoelectric element and the cap
can effectively be absorbed by the resiliency or elasticity of the
wire, so that a high degree of reliability of electrical conduction
is ensured. The resiliency or elasticity of the wire also serves to
accommodate any fluctuation in the size of the gap between the cap
and the piezoelectric element, thus affording a greater tolerance
for administration of dimensions. Furthermore, the wire, unlike the
conductive adhesive which tends to spread over a wide area, can be
fixed only to a limited portion of limited area on the
piezoelectric element, such as the nodal point or its vicinity,
thus posing minimum risk of impeding vibration of the piezoelectric
element.
FIGS. 19 and 20 show a tenth preferred embodiment of the present
invention.
In this preferred embodiment, a substrate 201 preferably has only
two patterned electrodes: namely, a pattern electrode 202 for input
and a pattern electrode 203 for output which extend externally out
of a metallic cap 220. Lead terminals 230, 231 are connected to
these externally led portions of the electrodes 202, 203 by
soldering as at 233 and 234. An upper electrode 211 of the
piezoelectric element 210 is connected to the inner surface of the
metallic cap 220 by a conductive adhesive 217, while a grounding
lead terminal 232 is connected to the external surface of the cap
220 by solder 235. The grounding lead terminal 232 is bent in the
thicknesswise direction of the substrate 201, so that the lead
portions of the thee lead terminals 230 to 232 are arranged in a
in-line manner.
In this preferred embodiment also, the substrate 201 and the cap
220 are preferably surrounded and coated integrally by a coating
resin (not shown).
In this tenth preferred embodiment, it is not necessary to form, in
one side edge of the substrate 201, a portion which would enable
connection of the lead terminals 230 to 232. In addition, the
pattern electrode for the grounding purpose can be eliminated. It
is therefore possible to reduce the dimensions, particularly the
height, of the substrate 1. In addition, since the metallic cap 220
is used as a wiring for interconnecting the upper electrode 211 of
the piezoelectric element 210 and the lead terminal 232, and since
a conductive adhesive 217 is used in place of conventional bonded
wire, it is possible to eliminate the wire boding operation, while
reducing impact applied to the element 210.
In place of the conductive adhesive 217 mentioned above, it is
possible to use other suitable connecting member or substance such
as a wire, conductive tape, solder, metallic spring or the like,
independently or in combination, for the purpose of interconnecting
the upper electrode 211 of the piezoelectric element 210 and the
metallic cap, depending on the size of the clearance between the
electrode 211 and the cap 220.
FIG. 21 shows a modification of the tenth preferred embodiment. In
this modification, the top central portion of the wall of the
metallic cap 220 is recessed inward and downward as at 220, and the
grounding lead terminal 232 is received in this recess and then
soldered as at 235. The soldering can easily be performed because
the lead terminal 232 is stably held in the recess 222 during the
soldering. The inward and downward recess 222 provides a
corresponding inward and downward projection projecting inward from
the top of the cap. A cream solder 218 may be applied to this
projection. After the cap 220 is placed on the substrate 201, the
cap is heated to the melting point of the solder, so that the upper
electrode 211 of the element 210 can easily be brought into
electrical connection with the cap 220. Obviously, the cream solder
may be substituted by a conductive adhesive such as that used in
the tenth preferred embodiment.
In this modification, the overall height or thickness of the
electronic part can be reduced because the lead terminal 232 is
fitted in the recess 222. In addition, the conductive agent (solder
or conductive adhesive) 218 concentrates to the projection, so that
undesirable spreading of the agent 218 over the wide area on the
element 210 can be avoided, despite any variation in the amount of
the conductive agent applied and in the size of the clearance
between the cap 220 and the upper electrode 211 of the element
210.
FIGS. 22 to 24 show another modification of the tenth preferred
embodiment. Only two pattern electrodes 202, 203: namely, an input
pattern electrode 202 and an output patterned electrode 203, are
disposed on the substrate 201. The outer ends of the electrodes 202
and 203 are extended to the underside or bottom surface of the
substrate 201 via through-hole grooves 201a formed in a side edge
of the substrate 201. Input and output lead terminals 230 and 231
are soldered to the ends 202a and 203a of the electrodes 202 and
203 which extend to the underside of the substrate 1. A grounding
lead terminal 232 is soldered as at 235 to the upper surface of the
metallic cap 220. The cap 220 may be provided at its top with a
recess for receiving the lead terminal 232 as in the first
modification described before.
The lead terminals 230 to 232 preferably have a round cross-section
and the ends 230a to 232a of these terminals are preferably
collapsed and flattened as shown in FIG. 24, thus facilitating
soldering to the electrodes 202, 203 and the cap 220. In order that
the lead terminals 230 to 232 are arranged in an in-line fashion,
the input and output lead terminals 230 and 231 are bent upward,
while the grounding lead terminal 232 is bent downward. The
substrate 201 and the cap 220 are surrounded and integrally
dip-coated with external coating resin 240. The bent portions of
the lead terminals 230 to 232 serve as a bank which prevents
spreading of the coating resin 40 to the outer side of the leads
beyond these bent portions. When the electronic component
(piezoelectric filter) is mounted on a printed circuit board with
the lead terminals inserted into corresponding holes formed in the
printed circuit board, these bent portions of the lead terminals
effectively serve to regulate the depth of insertion of the lead
terminals by abutting edges of the holes at the upper surface of
the printed circuit board. It is therefore possible to accurately
regulate the position of mounting of the electronic part on the
printed circuit board.
In this modification of the tenth preferred embodiment, the
connection of the input and output lead terminals 230, 231 is made
at the underside of the substrate 201, so that the longitudinal
dimension of the substrate 201 can be further reduced beyond that
in the first modification described before in connection with FIG.
21, thus contributing to a further reduction in the size of the
substrate 201. In addition, since the substrate 201 and the cap 220
are sandwiched at their upper and lower sides by the three lead
terminals 230 to 232, it is possible to temporarily hold the
electronic part by these lead terminals before and during the
soldering, thus offering improved efficiency of the soldering. In
addition, since a sufficiently large distance is preserved between
the cap 220 and the input and output lead terminals 230, 231, the
risk of shortcircuiting between these lead terminals and the cap
can be further reduced.
The described tenth preferred embodiment and its modifications are
only illustrative. For instance, the piezoelectric element may be
of the type which has only one electrode on each of the upper and
lower surfaces thereof, although the piezoelectric element used in
the tenth preferred embodiment has two electrodes provided on the
lower surface and one electrode on the upper surface of the
piezoelectric element. The circuit element may also be an element
other than a piezoelectric element such as a piezoelectric
resonator. Namely, the circuit element may be a capacitor or the
like element, or may be a circuit module. Obviously, the electronic
part to which the preferred embodiments of the present invention is
applied may be other electronic part than a piezoelectric filter,
e.g., a piezoelectric oscillator.
The number of the lead terminals also may be changed depending on
the number of the circuit elements and the number of the
electrodes. For example, the electronic part may have only two lead
terminals, or three or more lead terminals.
As will be understood from the foregoing description, according to
the tenth preferred embodiment and its modifications, a cap is
bonded to the substrate carrying a circuit element, so as to
completely seal the circuit element, without using any case having
openings for passing lead terminals. It is therefore possible to
easily produce an electronic part having lead terminals and
completely sealing a circuit element, whereby electronic parts are
obtained at reduced costs of production.
The element is mounted on the substrate, while the lead terminals
are connected to the substrate or the cap. Namely, the lead
terminals are not directly connected to the circuit element, so
that no substantial load is applied to the circuit element. This
conveniently reduces the risk of breakage of the element,
contributing to improvement in the throughput.
While the invention has been particularly shown and described with
reference to preferred embodiments thereof, it will be understood
by those skilled in the art that the foregoing and other changes in
form and details may be made therein without departing from the
spirit and scope of the invention.
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